May 12, 2010

Cell Biology This Week

This week marks the
start of a new (and hopefully fairly regular) series of posts on recently
published articles in cell biology.I
will provide some brief insight into why I mention a particular paper but this
is not meant to be a comprehensive resource, nor is it meant to comment on the
strengths or weaknesses of the studies.The goal is to let JCB readers know of recent work from other journals that
I think is noteworthy and to hopefully expand the scope of what people
traditionally think of as cell biology.With this disclaimer, read on….

In the May issue of Nature
Cell Biology, Urban et al. (2010) show that actin filaments in lamellipodia
are not branched.This is quite
surprising as it has been thought for a long time that the Arp2/3 complex
promotes the branching of filaments in these actin-rich structures at the
leading edge of cells.Urban et al.
examine lamellipodia in four different cell types using electron
tomography.This 3-D approach revealed
the presence of overlapping filaments rather than branched ones and indicates
that the previous observations of branched filaments might have been due to
technical artifacts.

In the May 7th issue of Science, Shields et al.
(2010) provide insight into how tumor cells evade the immune system.Tumor cells manipulate their microenvironment
or stroma to help their growth and dissemination.For example, tumor cells use macrophages in
their microenvironment to promote invasion and metastasis. I find this
relationship between cancer cells and the immune system quite fascinating.Now, Shields et al. show that tumors
secreting the cytokine CCL21 appear to create a microenvironment that mimics
the normal lymph node stroma--an environment that promotes immune
tolerance--thereby allowing the tumor cells to evade detection by the immune
system.

Finally, in the May 6th issue of Nature, Craven
et al. (2010) perform pronuclear transfer in human embryos in an interesting
study that I’m sure will be controversial.These investigators are interested in genetic disorders caused by
mutations in mitochondrial genomes that are usually maternally
transmitted.Using abnormal embryos from
a fertility clinic that have multiple nuclei at the one-cell stage, the authors
perform experimental manipulations that result in the formation of a recipient
zygote lacking a nucleus and two donor pronuclei that are surrounded by
membrane but lack mitochondria.They
then fuse the recipient zygote with the two donor cells and follow the
development for 6-8 days.Analysis of
the mitochondrial DNA revealed that it was largely from the recipient
zygote.The authors think that this kind
of an approach could be used eventually to prevent the transmission of
mitochondrial DNA diseases.

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